The present invention relates to an optical waveguide device suitable for a light source module, optical interconnection, optical communication, etc., and also to a manufacturing method for the optical waveguide device, an optical information processing device using the optical waveguide device, and electronic equipment using the optical information processing apparatus.
At present, signal transmission between semiconductor chips such as LSIs (large-scale integrated circuits) is generally made by electrical signals through board wiring. However, a data exchange amount required between the chips has remarkably increased with a recent higher functionality of MPU, resulting in the occurrence of various high-frequency problems. Such high-frequency problems typically include RC signal delay, impedance mismatch, EMC/EMI, and crosstalk.
To solve these problems, a packaging industry has mainly attempted to use various techniques such as optimization of wiring and placement and development of new materials.
However, the effects by the optimization of wiring and placement and the development of new materials have been blocked by physical limitations in recent years. Accordingly, for realization of higher functionality of a system in the future, it has now become necessary to reconsider the structure of a printed wiring board designed to simply package semiconductor chips. In recent years, various drastic measures against these problems have been proposed. Typical ones of the drastic measures are as follows:
(1) Finer Interconnection by Formation of a Multichip Module (MCM)
A high-performance chip is mounted on a precise mounting board such as a ceramic/silicon board, thereby realizing finer interconnection that cannot be formed on a motherboard (multilayer printed board). Accordingly, a wiring pitch can be reduced and a data exchange amount can therefore be greatly increased by increasing a bus width.
(2) Electrical Interconnection by Sealing and Integration of Various Semiconductor Chips
Various semiconductor chips are two-dimensionally sealed and integrated by using polyimide resin, and finer interconnection is made on such an integrated board. Accordingly, a wiring pitch can be reduced and a data exchange amount can therefore be greatly increased by increasing a bus width.
(3) Three-Dimensional Interconnection Between Semiconductor Chips
Through electrodes are formed in various semiconductor chips, and these semiconductor chips are attached together to form a multilayer structure. Accordingly, the interconnection between different kinds of semiconductor chips can be physically short-circuited, so that the problems including signal delay can be avoided. However, there arise other problems such as increased heating value due to the multilayering and thermal stress between the semiconductor chips.
Further, an optical transmission and coupling technique by optical wiring has been developed to realize high-speed and large-capacity signal exchange (e.g., “An Encounter with Optical Wiring”, Nikkei Electronics, pp. 122-125, FIGS. 4-7, (Dec. 3, 2001), and NTT R&D, vol. 48, no. 3, pp. 271-280 (1999)). Optical wiring is applicable to various places such as between electronic units, between boards in an electronic unit, and between chips on a board. FIG. 20 shows optical wiring for signal transmission between chips spaced a short distance. As shown in FIG. 20, an optical waveguide 51 is formed on a printed wiring board 57 on which the chips are mounted. This optical waveguide 51 is used as a transmission line for laser light or the like modulated by a signal, thereby allowing the construction of an optical transmission and communication system.
FIG. 21 shows the structure of the optical waveguide 51. As shown in FIG. 21, the optical waveguide 51 is composed of two claddings 54 and 55 and a core 56 sandwiched between these claddings 54 and 55. The core 56 has a pair of light incident and emergent portions 59a and 59b at the opposite ends. Each of the light incident and emergent portions 59a and 59b is formed as a 45° mirror surface. Further, the cladding 54 is integrally formed with a pair of lens portions 52 at positions respectively corresponding to the light incident and emergent portions 59a and 59b of the core 56.
A manufacturing method for the optical waveguide 51 will now be described with reference to FIGS. 22A to 22F.
As shown in FIG. 22A, a cladding 54 is filled into the cavity defined between an upper mold 53a and a lower mold 53b having in combination a shape corresponding to the cladding 54 with the lens portions 52, thus fabricating the cladding 54 by injection molding as shown in FIG. 22B. Accordingly, the lens portions 52 and the cladding 54 are integrally molded.
As shown in FIG. 22C, a core material 56a is filled into a mold 58. As shown in FIG. 22D, the cladding 54 with the lens portions 52 is attached to the upper surface of the mold 58 with the core material 56a interposed between the cladding 54 and the mold 58, and UV light is next applied to cure the core material 56a. As shown in FIG. 22E, the mold 58 is removed to obtain a laminated structure composed of the cladding 54 and the core 56.
Finally, as shown in FIG. 22F, another cladding 55 previously fabricated by injection molding or the like is bonded to the cladding 55 of the above laminated structure, thus obtaining the optical waveguide 51.
In the conventional optical waveguide and the manufacturing method therefor as shown in FIGS. 21 and 22A to 22F, the lens portions 52 and the cladding 54 are integrally molded by using the upper and lower molds 53a and 53b. Accordingly, the positions of the lens portions 52 are decided in this molding step, and the alignment between the light incident and emergent portions 59a and 59b of the core 56 and the lens portions 52 becomes difficult. As a result, there is a possibility of reduction in alignment accuracy and yield.